Duplicate bill check before payment

Find the bills in this payment run that you already paid, or are about to pay twice.

Load the bills you are about to pay and your paid or history bills as CSV or XLSX, including QuickBooks vendor reports. DuplicateBillCheck compares every bill with the same vendor and currency, requires the exact amount for a likely duplicate, matches invoice numbers conservatively and shows the source rows behind every result.

Check bills Try the demo Download CSV templates

Files never leave your browser. The check runs on your device; bills, vendor names and files are never uploaded.
First 25 bills free, with CSV. Batch-wide totals always free. No account.
$49 once per batch for every bill, the full CSV, a printable report and re-checks against new or corrected history files.

Illustrative example: one bill in the demo

Bill to pay	Northwind Packaging LLC · INV-004812	$1,240.00
Paid bill in history	Northwind Packaging LLC · 4812 · Paid	$1,240.00
Would be paid twice		$1,240.00

Likely duplicate: already paid Same vendor, currency and amount; INV-004812 = 4812 after normalization
Likely duplicate within this batch Bluebird Office Supply 77310 and 0077310, $212.40 each
Possible match: review SIT-1009 is in history at $1,450.00, the batch has $1,500.00
No match found November rent: same vendor and amount as October, different invoice number

Example figures from the demo; your results depend on your files. A result describes the files, not proof that a bill was or was not paid.

Check your bills

Loading…

How it works

Export the bills to pay. The batch you are about to pay: vendor, invoice_number, bill_date, amount (start from the bills to pay template), or a QuickBooks Unpaid Bills or vendor report as CSV or XLSX.
Export the paid or history bills. Bills already entered or paid, ideally with a status or paid_date column (paid bills template). QuickBooks vendor reports are read as they are: title lines, vendor group rows and Total rows are recognized, and Num, Date, Transaction Type, Open Balance map to the right columns.
Check on your device. Each bill to pay is compared with every history bill and every other bill in the batch that has the same vendor and currency.
Review before you pay. Every result lists the matching bills, the reasons and the raw lines they came from. Hold the likely duplicates, review the possible ones, then print the report or hand over the CSV.

What DuplicateBillCheck reports

Likely duplicate: already paid

A history bill with the same vendor, currency, exact amount and invoice number is explicitly marked paid (its own status column says Paid, or it has a paid date).

Likely duplicate: in history, not marked paid

The same bill is already in your history file, but the file does not say it was paid: the status is unknown (no status column or a blank status) or open. Paid and unknown are always kept apart.

Likely duplicate within this batch

Two or more bills in the batch itself have the same vendor, currency, amount and invoice number. Verify the original bill before paying.

Possible match: review

Same vendor and currency, but not identical: the same invoice number with a different amount, the same amount with no invoice number to compare and bill dates within 45 days, or the same amount and date with different invoice numbers.

Invalid row: not checked

Rows with no vendor, impossible or ambiguous dates (11/31/2026, 03/04/2026 in a mixed file), amounts that are not plain numbers, or zero amounts are flagged and never guessed.

No match found

No history bill and no other bill in the batch matches under the rules.

Strict on purpose

Vendor, currency and exact amount safeguards. Bills are compared only within the same vendor (case, punctuation and suffixes such as Inc or LLC ignored) and currency. A likely duplicate needs the exact amount in cents.
Conservative invoice numbers. Case, spaces, separators, an INV prefix and leading zeros of a numeric invoice are ignored: INV-004812 = 4812. A-4812 is not 4812.
Paid is never inferred from a bill row. Only an explicit status or paid date makes a history bill paid. Payment rows (Bill Payment, Check) are never linked to bills.
The same explicit bill ID in both files is the same record, not a duplicate. All money math uses exact integer cents; text from your files is shown as plain text, and the CSV export neutralizes spreadsheet formulas.

Files it reads

CSV with comma, semicolon, tab or pipe delimiters, quoted values and UTF-8 or UTF-16; XLSX (the first sheet, real Excel dates included). Legacy .xls: save as XLSX or CSV first.
Header discovery: the header row is found in the first 40 lines, so report titles, company names and date ranges above it are skipped.
QuickBooks vendor report aliases: Num, Ref No., Bill No. → invoice number; Date → bill date; Name, Vendor, Payee, Supplier → vendor; Transaction Type, Due Date, Open Balance, Memo/Description, Status, Payment Status. With no vendor column, vendor names come from the group rows above each block.
Date validation: YYYY-MM-DD, MM/DD/YYYY or DD/MM/YYYY decided once per file (US month-first when the file does not prove otherwise, or set it yourself), and month names. Impossible dates are rejected.
Samples: bills to pay (CSV), bills to pay (XLSX), QuickBooks-style paid bills report.

Pricing

Free

Unlimited checks on your device
Batch-wide totals and result counts
The first 25 bills to pay in detail, plus a CSV of those 25
Demo batch, sample files and CSV templates

Full batch report

$49 USD, once per batch

Every bill to pay on screen and in the CSV
Printable report with matched bills and source rows (print or save as PDF)
Re-check the same batch against new or corrected paid/history files
No subscription; pay with card (Square) or PayPal

A purchase is bound to the bills-to-pay file of its batch through a one-way SHA-256 fingerprint computed in your browser. A different batch file needs its own purchase.